In the area of graphical user interfaces (GUI), a tabbed document interface (TDI) is one that allows multiple documents to be contained within a single window, using tabs as a navigational widget for switching between sets of documents. TDI is an interface style most commonly associated with web browsers, web applications, text editors, and preference panes. In keeping with the desktop metaphor, GUI tabs are modeled after traditional card tabs inserted in paper files or card indexes.
Software as a service (SaaS), also referred to as “on-demand software,” is a software delivery model in which software and its associated data are hosted centrally (e.g., in the Internet) and are typically accessed by users using a thin client, such as using a web browser over the Internet. SaaS has become a common delivery model for most business applications, including accounting, collaboration, customer relationship management (CRM), enterprise resource planning (ERP), invoicing, human resource management (HRM), content management (CM) and service desk management. Whether in an online configuration or a desktop configuration, SaaS products often use a purchasing model that entails offering a core set of functionality (often for free with SaaS subscription) and allowing the user to pay for additional functionality modules from a selection menu.